Welcome to Jornadas Doutorais do Departamento De Física!
We are excited to announce the 2023 Jornadas de Doutoramento do Departamento de Física! Jornadas will occur on the afternoons of the 29th and 30th of March 2023 in room Sala de Atos (6.2.56), Building C6.
We are organizing an action-packed event where you will have the opportunity to get to know the latest that is being made in Ciências, showcase your work and, above all, meet and discuss ideas with your department PhD colleagues! We are expecting a massive turn-out.
The Jornadas will feature two different modes of participation:
> Oral presentations (10 min) concerning your PhD work;
> Posters to show your work during coffee-breaks, together with a time for a flash (1 min) presentation.
Keynote speakers, relevant both in academia and the industry, will also participate in the event alongside you. You will have a chance to get to know their work and impress them with your presentation/poster!
Additionally, there will be short video interviews of former PhD students sharing with us their journey after completing their PhD.
A novelty this year, we are organizing a dinner where we can better know our colleagues in a more informal environment.
Patrícia Muiño graduated in Physics and obtained her PhD in Particle Physics from the Universidade de Santiago de Compostela. She has been a research fellow at DESY and at CERN. She is an assistant professor at Instituto Superior Técnico (IST), a researcher at LIP, the coordinator of the Portuguese ATLAS Group, and the Portuguese representative at the European Committee for Future Accelerators.
Zita Martins graduated in Chemistry at Instituto Superior Técnico (IST) and obtained a PhD in Astrobiology at the University of Leiden (Netherlands). She is an Associate Professor at IST and Co-Director of the MIT-Portugal Program (MPP). She actively participates in projects of the European Space Agency (ESA) and is an Advisor for Science, Innovation and Digital Transition for the Presidency of Portugal.
Paulo Ferreira graduated in Technological Physics from the Faculdade de Ciências da Universidade de Lisboa, and got his PhD in Electrical and Computer Engineering from the Instituto Superior Técnico (IST). He has worked in medical physics at the Instituto Português de Oncologia de Lisboa de Francisco Gentil (IPOLFG). He is currently working in the Champalimaud Foundation.
Luís Cabrita graduated at FCT-UNL in Applied Chemistry – Organic Chemistry. During his PhD he studied anthocyanins at Univ. Bergen, Norway. During several years he did research at FCT-UNL and Inst. Politécnico Bragança. He was the founder of a start-up, Biocolour, and worked for the pharmaceutical industry. Since 2015 he is responsible for the Department of Product Engineering at Amorim Cork Research.
Modelling extraction and retention in porous media: how to extract the perfect coffee part 3
Several natural and industrial processes involve the extraction or retention of a solute by a fluid invading a network of channels. Examples include aquifer contamination, chemical filtration, and coffee extraction. We propose a continuum equation to model these processes, parametrized by the Péclet number and the rate of mass transfer between the solid and the fluid. We study the time dependence of the extracted mass for different values of the parameter space. The continuum description is validated by combining computational fluid dynamics and experiments with coffee. An analytical solution is derived for the limit of slow mass transfer, which is corroborated by numerical simulations.
Building a Microchip Laser for ESA: an overview of an engineering journey
The building of a laser device needs to consider numerous factors and their interplays. Pumping generates heat both in the active medium and the pumping source itself. The mechanical design influences how that heat can be dissipated throughout the device but must also allow for the delicate positioning of support optics and most importantly the alignment of the laser cavity. The existing mathematical models provide an insight into the dynamics of the laser system but must be carefully be balanced with experimentation as producing a representative model may require more factors than can be implemented in a reasonable time frame. Designing equipment for the space sector also carries its set of additional requirements. Low mass and low power consumption systems are preferred and the demanding environmental factors of space operation must be accounted for such as vacuum, radiation, the mechanical forces involved in launching and temperature range.
Stabilization of calibration light sources for High Accuracy Photometry Instruments
Transit spectroscopy and multi-band photometry has been so far conducted using general-purpose, space-based instruments. These measurements however suffer from a high level of systematic error due to issues such as pointing jitter, thermal and opto-mechanical stability, wavelength and photometric calibration, and detector stability. Testing and calibration of high precision photometers for the detection of planetary transits requires a light source which photometric stability must be better than the goal stability of the photometer to be tested. In case test, integration and calibration of these sensors, it will be required highly radiometrically stable light sources, both in flux and spectra. The proposed project aims to research and develop a device that senses the light source fluctuations and modulates the beam, both in flux and in spectra, to produce a sufficiently stable source, a truly impressive challenge when stabilization levels of few ppm are required up to several hours of observation.
Venus Atmospheric Dynamics: Akatsuki UVI and TNG HARPS-N observations
Venus is a key planet in the understanding of planetary evolution to which the study of the atmospheric dynamics and better understanding of cloud circulation is indispensable. To describe Venus’ atmospheric circulation, this work employed two methods to obtain wind velocities on specific layers of the Venusian atmosphere: The Doppler velocimetry, a technique based on solar light scattered on Venus’ dayside which provides instantaneous wind velocities measurements as described in the works of Pedro Machado, and the cloud-tracking method which consists of a simple analysis of a pair of navigated and processed images by matching specific points in both, allowing us to deduct an average velocity for a certain cloud layer of the atmosphere. In short, the main goal of this work was to build wind profiles in different wavelengths which allow us to analyse several layers of the Venusian atmosphere and the temporal evolution of the wind velocities.
Shape transitions of sedimenting fluid-filled bodies
The hydrodynamics and deformation of fluid-filled bodies such as droplets, capsules, etc constitutes an important problem with various uses . Capsules can be found in nature, for example in the form of cells which is of importance in pharmaceutical and bioengineering industries. The environment may also have a strong effect on the dynamics of bodies. We investigate shape transitions of sedimenting deformable bodies in a quiescent viscous fluid inside a confined channel. The deformation occurs in the initial states of motion, after which it reaches a steady state shape. In general, we notice three steady state regimes: an oblate-like shape perpendicular to the direction of motion, a quasi-circular shape and a bullet-like shape. We further analyze the hydrodynamic stresses and forces responsible for this shape transition.
E Coli, now also available in 3 dimensions.
A Complete Characterisation of Ultra Steep Spectrum Sources in the COSMOS Field
Ultra Steep Spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (𝑧 > 2)(Afonso et al. (2011)). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to new sensitivity levels, thanks to a transformation at the generation of radio surveys currently being produced. Combining recent observations from MIGHTEE (the MeerKAT International Gigahertz Tiered Extragalactic Explorations; (Jarvis et al. (2016a)), one of MeerKAT’s flagship Large Survey Projects, and VLASS (the Very Large Array Sky Survey) we founded more than 500 USS, all with optical counterparts, ie. with spectroscopic redshift and photometric redshift when available. The aim of this paper is to find a good method to characterize distant galaxies. Using a USS criterion, combining with other methods, to have a good sample of distant galaxies at the COSMOS field, using a early data from MeerKAT. We used data from MeerKAT radio telescope at 1.28GHz (Delhaize et al. (2021)) and VLA 3GHz (Novak et al. (2015a)). Using the comprehensive multi-wavelength dataset available over this area, we are able to extensively characterize this sample, and explore the usefulness and efficiency of the USS radio criteria to reach the highest redshifts at the faintest radio fluxes — a potentially powerful tool to further explore on the upcoming Square Kilometer Array era. This work developed a sample for USS much larger than the previous ones, due to the great sensitivity of MeerKAT. We have assembled a large sample of over 546 USS radio sources in the COSMOS field, reaching well into the mJy radio regime. We have a significant sample of distant galaxies with optical and infrared wavelength counterparts. These sources show a correlation between their spectral index and redshift, to include a K[mag] criteria filter can be a imperative steep to find high redshift galaxies. Our results show that, USS is a method to find distant galaxies but, considering a strongly influence with other criteria. Proven a new data from Endsley et al. (2022) with a galaxie with a photometric 𝑧 ∼7 demonstrates that our work can be really usable. This source was founded in our work and confirming the methodology.
Testing Unified Dark matter-energy models against structure formation
Cosmological observations strongly support the idea that the expansion of the universe is currently accelerating. In this talk I will present the work of testing an Unified Dark Matter-Energy model in the non-linear regime. Starting from a linear implementation in the Boltzmann code CLASS of an UDM model tested against weak lensing, CMB, Sne IA and BAO, we focus on a simpler UDM model lagrangian to be implemented as first test in an N-Body DM simulation code. I will show the results of the linear analysis, how the UDM model is being implemented in the non linear regime and present a spherical solution for the model as a test to validate the implementation of the model in the N-Body code.
Scintillating array for real–time high–resolution dosimetry
Radiobiology is a multidisciplinary area where the effects of radiation in cells, tissues and organs are studied. To understand the biological effects of radiation it’s important to have a measurement of the energy deposition at the micro or even nano-scale. Bearing this in mind, this project is focused in the development of a detector that offers radiobiology researchers the possibility to achieve real-time dose measurement at this scales. The technique chosen resorts to scintillation dosimetry with plastic optical fibers. The optical fibers offer a very good spatial resolution down to 0.25 mm and good tissue equivalence. In this work we present the inital design of the detector, ready for construction. The detector will be built as an irradiation box with a sensitive area composed of an array of plastic optical fibers with the possibility of mapping dose in one plane or in two orthogonal planes.
Oxytocin’s role on central and autonomic neurocorrelates of salience attribution – evidence from pupillometry and eye-gaze
To describe the overarching effects of Oxytocin on human social cognition, the social salience hypothesis posits the neuropeptide to increase salience towards social relevant/rewarding stimuli. Yet, it is still unclear whether this salience attribution to social stimuli arises from them being inherently more rewarding than non-social. To clarify this, we conducted an intranasal Oxytocin, double-blind, placebo-controlled study while recording participants’ pupil dilation and eye gaze during a reinforcement learning Social Salience Attribution Test that orthogonalizes the social and reward value of stimuli. We found Oxytocin, but not placebo, to increase pupil dilation towards rewarding stimuli (vs non-rewarding) before reinforcement feedback, and crucially, this difference started sooner for social stimuli (vs non-social). These findings were corroborated by eye-gaze analysis and altogether suggest that Oxytocin facilitates learning, and increases salience, of rewarding stimuli irrespective of their socialness, yet it does so more for social than non-social stimuli.
Spherical collapse in shift symmetric Galileon theory
Given the lingering theoretical issues and observational tensions surrounding the current standard cosmological model (LCDM), several alternative theories, where the gravitational interaction is modified on cosmological scales, have been put forward. These proposals, known as Modified Gravity (MG) theories, often introduce additional degrees of freedom (dofs), such as scalar fields, that can couple to Standard Model fields and end up mediating a fifth force between matter sources. Since General Relativity has been extremely well tested on local scales and no new dofs have been detected, MG theories must be equipped with a screening mechanism capable of suppressing the modifications to gravity on these scales. These mechanisms play an important role during the process of formation of gravitationally bound structures. In this talk I will present the study of non-linear growth of large scale structures using the spherical collapse approach in the particular case of the Kinetic Gravity Braiding (KGB) theory by using a general approach for its description. I will investigate the latter’s effects on some core physical quantities of the spherical collapse model and also present predictions for the evolution of the halo mass function.
Radiotherapy enhanced with gold nanoparticles: impact of physical parameters on GBM survival curves
The combination of high-Z nanoparticles and radiotherapy leads to an increased radiation effect in tumoral cells without increasing the patient dose. We review the impact of physical parameters, as gold nanoparticle (AuNPs) radius and concentration, in the cell survival curves by applying a version of the Local Effect Model in the presence of AuNPs. A method to reconstruct confocal microscopy images that allows using voxelized realistic cell geometries in MC simulations using TOPAS is presented. The simulations were benchmarked against Co-60 irradiations. No clear trend is observed in the dose effect as a function of the gold mass in the cytoplasm when the AuNP radius is kept constant. The same lack of trend is observed when the gold mass inside is kept constant, but the AuNP radius varies. For a constant number of NPs there is a critical radius above which the dose effect increases significantly. This effect is more significant when the NPs are close to the nucleus. These results suggest there is a balance between the increase in radiation and the shielding produced by the NPs.
Recent simulation advances on the folding of knotted proteins
We present an off-lattice Monte Carlo simulation method to study the folding transition of knotted proteins that efficiently samples thermal equilibrium distributions. We combine it with a method that identifies the native and non-native interactions that stabilize equilibrium knotted states. Interestingly, our results suggest that these non-native interactions are also the ones that drive faster kinetics of knot formation.
Reanalyzing Jupiter ISO/SWS data through a more recent atmospheric model
The study of isotopic ratios in the atmospheres of planets gives an insight into the formation history and evolution of these objects. The more we can constrain these ratios the better we can understand the history and future of our Solar System. To help in this endeavour, we used ISO/SWS Jupiter observations in the 793-1500 cm−1 region and retrieved the temperature-pressure profile and the chemical abundance profile for various chemical species with the NEMESIS radiative transfer retrieval code, obtaining a best fit synthetic spectrum with a χ2/N = 0.86. From the retrieved methane abundance profiles, we performed the isotopic ratio study, obtaining a 12C/13C ratio of 79 ± 27 and a D/H ratio of (3.1 ± 0.8) × 10−5, with these ratios being consistent with other published results from literature.
LIDAR systems for Near-Earth Object Observation
Near-Earth Objects (NEO) are the topic of several research studies, with objects smaller than 1km in size posing the most threats and being the less understood of this scientific domain. The Asteroid Impact and Deflection Assessment (AIDA) mission involves NASA and ESA with the main mission goal to perform and analyze the asteroid deflection using the Kinetic Impactor technique. The mission target is Didymoon, a moon of a binary asteroid called Didymos. NASA oversees the Double Asteroid Redirection Test (DART probe), and ESA is responsible for HERA probe, that will measure the Dydimoon deflection caused by the impact. The LIDAR is a time-of-flight altimeter instrument that will measure the distances from the HERA spacecraft to the target. The LIDAR has a compact design and needs to withstand extreme conditions, such as radiative and thermal conditions, without compromise its high accuracy measurements. It provides information for a 3D topographic mapping and calculates the asteroid reflectivity. The measurements are to be performed at a distance from 500 m to 14 km while operations such as fly byes or landings remain a possibility.
Advances in Glioblastoma treatment
Glioblastoma multiforme (GBM) remains a challenging disease, being the most common and deadly brain tumour in adults, with no curative solution and overall short survival time. This incurability and short survival time means that, despite its rarity (average incidence of 3.2 per 100,000 persons), there has been an increased effort to try to treat this disease. Standard of care in newly diagnosed glioblastoma is maximal tumour resection, followed by initial concomitant radiotherapy and temozolomide (TMZ), and then further chemotherapy with TMZ. Imaging techniques are key not only to diagnose the extent of the affected tissue, but also for surgery planning and even for intraoperative use. Eligible patients may combine TMZ with Tumour Treating Fields (TTF) therapy, which delivers low-intensity and intermediate frequency electric fields to arrest tumour growth. Nonetheless, the blood-brain barrier (BBB) and systemic side effects are obstacles to successful chemotherapy in GBM.
Development of a System for Mental Workload Assessment
Percolation-based simulation to predict caking kinetics of polydisperse amorphous powders
The shelf life of powder-based food products is usually limited by the dynamics of caking.Individual particles absorb water vapor, which triggers the formation of sinter bridges and the growth of lumps of particles, affecting the mechanical properties and perceived quality of the powder. Previous models of caking have focused on the dynamics at the particle level. To study the impact on global connectivity and mechanical properties, we mapped caking into a ranked percolation model where the formation of bridges is a non-trivial function of space and time. Since this threshold only depends on the geometry of the granular assembly, we can separate the contribution of the spatial heterogeneities and of the individual particle properties. This enables rational approach for interpreting and mitigating caking propensity of commercial products consisting of particle species with different particle size distributions. We corroborate the numerical and analytical predictions with experiments.
Brown dwarfs as testbeds for star and planet formation
Brown dwarfs (BDs) lie in the substellar mass regime, and are a bridge between stars and planets, thus providing a unique window into the unknowns of their formation processes. The dominant mechanism behind the formation of BDs is still not fully constrained. In fact, BD formation is expected to be affected by the environment in which they are born, in particular, an environment with high stellar densities and/or large number of massive stars would increase the efficiency of BD production compared to stars. In order to test these hypotheses, we are studying the low-mass population of massive young clusters with extreme environmental properties compared with nearby star-forming regions. One of these clusters is NGC 2244 (d=1.5 kpc), which hosts a large number of OB stars and presents a low stellar density. We have built a robust sample of cluster members using deep photometry, astrometry and multi-object spectroscopy (VIMOS and KMOS/VLT), resulting in the first spectroscopically confirmed BDs beyond 1 kpc. In this talk, I will present the work I have developed in my thesis where I have developed a new method for spectroscopic analysis of cool dwarf spectra in the near infrared, implementing machine learning models to efficiently separate young members from field contaminants. Furthermore, I will present our results on the BD population of NGC 2244 where we found the first ever potential evidence of OB stars affecting the formation of BDs. I will also compare these results with the other massive clusters in our sample, as well as with nearby star-forming regions.